Micro-cellular closed-cell sponge rubber outers

ABSTRACT

The invention relates to a method of making an outer tire layer on a pneumatic tire microcellular closed-cell sponge rubber, method of making the aforesaid product.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. National Stage Application of International ApplicationNo. PCT/USO1/43636, International Filing Date Nov. 14, 2001, whichclaims benefit of U.S. Provisional Patent Application. Ser. No.60/248,401 filed Nov. 14. 2000.

FIELD OF THE INVENTION

The field of the present invention is rubber outer layers, andspecifically micro-cellular closed-cell sponge rubber outer layers forpneumatic tires, shoe soles and other applications.

BACKGROUND OF THE INVENTION

According to conventional philosophies, pneumatic rubber tire outers aremade exclusively of a relatively hard durable solid rubber. However, thecharacteristics of relatively hard non-sponge (“solid”) rubber do notfavorably support the special needs of certain sports vehicles, such asmountain bikes, bicycle motorcross (“bmx”) vehicles, cross-countrybicycles, All Terrain Vehicles (“ATV”), and go-carts. Similarly, thecharacteristics of relatively hard solid rubber do not favorably supportthe needs of certain other types of special vehicles, including forexample, wheelchairs, baby joggers, skateboards, rollerblades, scooters,motorcross vehicles, and others.

Pneumatic mountain bicycle tire outers have conventionally been madewith relatively hard durable solid rubber. Relatively hard durable solidrubber is used in making the outers for such tires under theconventional thinking that because a mountain biking tire is subjectedto high-friction conditions, the characteristics of relatively harddurable solid rubber will provide long wear.

There are a number of problems, however, with such tires. For example,relatively hard solid rubber does not have a high-frictioncoefficient—in most cases, the harder the rubber, the lower the frictioncoefficient of the rubber. Therefore, most conventional relatively hardsolid rubber tires do not provide good traction characteristics.

Another problem with pneumatic tires made with relatively hard solidrubber outers is that they do not exhibit good shock absorptioncharacteristics. In the case of mountain bikes, shock absorption is acritical factor in the design of such bikes. Mountain bikes can cost tentimes the amount of a regular street bicycle—much of the cost beingdevoted to providing highly-advanced shock absorption characteristics tovarious structural features of the bicycle. After spending thousands ofdollars on a highly-advanced shock absorbing bike frame, the mountainbiker then mounts pneumatic tires made of relatively hard solid rubberthat characteristically exhibit low shock-dampening characteristics—thatis, they bounce.

Soft rubber exhibits higher-friction coefficient characteristics thanharder rubber. However, soft rubber does not wear well and further doesnot exhibit significantly reduced dampening characteristics as comparedto harder rubber.

Sponge rubber exhibits high-dampening and high-friction coefficientcharacteristics. However, a sponge rubber made using very soft rubberwould not exhibit durability characteristics necessary for pneumatictires.

As with pneumatic tire rubber outers, rubber outers, that is, an outerlayer of rubber, in other applications that are often subjected tohigh-wear, high-friction conditions, such as, for example, shoe soleouters, are often made with relatively hard durable solid rubberaccording to the conventional thinking that the relatively hard durablesolid rubber will provide long wear. However, as with tires, shoe soleouters (outsoles) and other rubber outers made according to thisconventional thinking do not exhibit high-friction coefficient orshock-absorbing characteristics.

SUMMARY OF THE INVENTION

The present invention provides a method for formulating with relativelyhard solid rubber, a micro-cellular closed-cell sponge rubber outer suchas for use as an outer tire layer (a “tire outer”) on pneumatic tires orfor use as a component of shoe sole outers, said method comprisingblowing a relatively hard non-sponge (or “solid”) rubber having a firsthardness scale measurement with a micro-cellular closed-cell inducingblowing agent to produce a micro-cellular closed-cell sponge rubber witha second hardness scale measurement, wherein the second hardness scalemeasurement is less than the first hardness scale measurement.

The term “outer” is used herein to mean an outer layer. In the case ofpneumatic tires, an outer layer of rubber (a tire “outer”) is bonded toa non-stretch or limited-stretch pneumatic tire lining. In the case ofshoe soles, an outer layer of shoe sole material (a shoe sole outer,sometimes referred to in the shoe industry as an outsole) is fastened orvulcanized to a shoe upper, or is fastened or vulcanized to a midsoleand shoe upper. The way in which a tire outer is fastened to a pneumatictire lining is not a limitation of the present invention. The way inwhich a shoe sole outer is fastened or vulcanized to a shoe upper, or toa midsole and shoe upper, or to any other inner-sole, midsole, and shoeupper configuration is not a limitation of the present invention.

The words “non-sponge” and “solid” are used interchangeably in thedisclosure of this invention. It will be understood by someone withordinary skill in the art that blowing a relatively hard non-spongesolid rubber with a micro-cellular closed-cell inducing blowing agentwill produce a micro-cellular closed-cell rubber having higher dampeningcharacteristics and a higher friction coefficient than the solid rubberfrom which the sponge rubber is produced. An outer tire layer soformulated would be for use on pneumatic tires for any of a variety ofvehicles, including but not limited to: mountain bikes, cross-countrybicycles, All Terrain Vehicles (“ATV”), off-road vehicles, go-carts,wheelchairs, baby joggers, skateboards, rollerblades, scooters,motorcross vehicles, and others.

The present invention also provides a method for manufacturing pneumaticrubber tires, said method comprising vulcanizing an outer tire layer ofmicro-cellular closed-cell sponge rubber formulated from relatively hardnon-sponge rubber, and bonding the outer tire layer to a non-stretch orlimited-stretch pneumatic tire lining. Pneumatic tire linings, oftenmade of nylon material, are sometimes referred to as “non-stretch.”However, it will be understood by someone with ordinary skill in the artof tire making that nylon and other pneumatic tire lining material“stretch” to a limited extent. Therefore, reference herein to“non-stretch” or “limited-stretch” pneumatic tire lining material meanspneumatic tire lining material, such as nylon, that stretches only to alimited extent.

The present invention also provides a method for manufacturing pneumaticrubber tires, said method comprising vulcanizing an outer tire layercomprising micro-cellular closed-cell sponge rubber formulated fromrelatively hard non-sponge rubber, said outer tire layer furthercomprising non-sponge rubber, and bonding the outer tire layer to anon-stretch or limited-stretch pneumatic tire lining.

The present invention provides a method for manufacturing pneumaticrubber tires, said method comprising molding an outer tire layer ofmicro-cellular closed-cell sponge rubber formulated from relatively hardnon-sponge rubber, and bonding the molded outer tire layer to anon-stretch or limited-stretch pneumatic tire lining.

The present invention further provides a method for manufacturingpneumatic rubber tires, said method comprising bonding an outer tirelayer of micro-cellular closed-cell sponge rubber formulated fromrelatively hard non-sponge rubber to a non-stretch or limited-stretchpneumatic tire lining.

The present invention further provides a method for manufacturingpneumatic rubber tires, said method comprising bonding an outer tirelayer comprising micro-cellular closed-cell sponge rubber formulatedfrom relatively hard non-sponge rubber and further comprising non-spongerubber, to a non-stretch or limited-stretch pneumatic tire lining. Thepresent invention also provides a pneumatic rubber tire, said pneumaticrubber tire comprising an outer tire layer comprising micro-cellularclosed-cell sponge rubber formulated from relatively hard non-spongerubber wherein the outer tire layer is bonded to a non-stretch, orlimited-stretch, pneumatic tire lining.

The present invention also provides a pneumatic rubber tire, saidpneumatic rubber tire comprising an outer tire layer comprisingmicro-cellular closed-cell sponge rubber formulated from relatively hardnon-sponge rubber and further comprising non-sponge rubber wherein theouter tire layer is bonded to a non-stretch, or limited-stretch,pneumatic tire lining.

The present invention further provides a method for manufacturing shoesole outers, said method comprising vulcanizing micro-cellularclosed-cell sponge rubber formulated from relatively hard non-spongerubber with non-sponge rubber in a shoe sole outer mold.

The present invention further provides a shoe sole outer (also sometimesreferred to as an outsole), said shoe sole outer comprisingmicro-cellular closed-cell sponge rubber formulated from relatively hardnon-sponge rubber and further comprising non-sponge rubber.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present invention are more fully setforth in the following description of exemplary embodiments of theinvention. The description is presented with reference to theaccompanying drawings in which:

FIG. 1 is a high level flow diagram depicting the logic steps todetermining a proportion of blowing and a rubber formulation with whichto manufacture a rubber for a particular intended purpose;

FIG. 2 is a graphic representation that depicts, under extrememagnification, an exemplary uneven density distribution of gas pocketsthat sometimes results from micro-cellular, closed-cell sponge rubbervulcanization;

FIG. 3 is a cross-sectional view of an exemplary outer tire mold intowhich rubber is placed to form a tire outer in an exemplary embodimentof the present invention;

FIG. 4 is a cross-sectional view of an exemplary single-rubber tireouter in which micro-cellular closed-cell sponge rubber forms a tireouter in an exemplary single-rubber tire outer embodiment of the presentinvention;

FIG. 5 is a cross-sectional view of an exemplary multi-rubber tire outerin which non-sponge rubber forms outer tire tread lugs andmicro-cellular closed-cell sponge rubber forms inner tire tread lugs ina first exemplary multi-rubber tire outer embodiment of the presentinvention;

FIG. 6 is a cross-sectional view of an exemplary multi-rubber tire outerin which non-sponge rubber forms inner tire tread lugs micro-cellularclosed-cell sponge rubber forms outer tire tread lugs in a secondexemplary multi-rubber tire outer embodiment of the present invention;

FIG. 7 is a cross-sectional view of an exemplary assembled bicycle tirecomprising a multi-rubber tire outer in a first alternative exemplaryembodiment of the present invention;

FIG. 8 is a top view of an exemplary shoe mold;

FIG. 9 is a cross-sectional view of a portion of the exemplary shoemold;

FIG. 10 is a cross-sectional view of a portion of an exemplary shoe soleouter comprising micro-cellular closed-cell sponge rubber and non-spongerubber; and

FIG. 11 is a bottom view of an exemplary shoe sole outer comprisingmicro-cellular closed-cell sponge rubber and non-sponge rubber.

DETAILED DESCRIPTION OF THE INVENTION

The making of sponge rubber is well known in the art of rubber making.One of a variety of “blowing agents” is used in the rubber formulationprocess to create a multitude of gas pockets in the final rubberproduct.

Instead of using soft rubber, according to the present invention,blowing agents are added to relatively hard solid rubber formulations tocreate a relatively hard rubber sponge rubber. The relatively hardrubber sponge rubber is then used to make an outer tire layer forpneumatic tires. The exemplary description of methods of formulatingrelatively hard rubber sponge rubber for, and manufacturing, a mountainbike tire is illustrative and is not a limitation of the invention.

Various blowing agents provide different types of results. Proportionsbeing equal, some blowing agents tend to create a smaller number of, butlarge-sized, air or gas pockets; whereas other blowing agents tend tocreate a higher number of, but smaller-sized air or gas pockets.

Some blowing agents produce what is known in the art as “open cell”sponge. Such blowing agents produce air pockets that are open. Such openair pockets can be useful when the rubber is intended for waterabsorption products.

Other blowing agents produce what is known as “closed cell” sponge. Suchblowing agents produce gas pockets in rubber such that each gas pocketis encapsulated with the rubber.

The present invention provides that blowing agents that producemicro-cellular, closed-cell sponge are used to “blow” relatively hardsolid rubber. The book entitled Blue Book 1997: Materials, compoundingingredients, machinery and services for the rubber industry, Job H.Lippincott publisher, published by Rubber World magazine, a Lippincott &Peto publication, contains a list of rubber blowing agents on pages312-318, the factual content of which is incorporated by referenceherein for all purposes as if fully stated here and selected portions ofthe factual content of which are provided below.

The Blue Book lists a number of blowing agents by Tradename, compositionand Supplier; properties and function and compounding are described foreach blowing agent listed. The Blue Book list of Blowing Agents isextensive. Accordingly, exemplary blowing agent compositions areidentified below. The following list of exemplary micro-cellular,closed-cell sponge inducing blowing agent compositions is illustrativeand is not a limitation of the blowing agents that can be used in thepresent invention.

Exemplary blowing agent compositions listed in the Blue Book thatproduce microcellular, closed-cell sponge include: Azodicarbonamide(including Activated and Modified forms), p-toluene sulfonylhydrazide(TSH), Sodium bicarbonate and Dinitroso pentamethylene tetramine (DNPT).Someone with ordinary skill in the art of rubber making will understandthat use of other micro-cellular, closed-cell sponge inducing blowingagent compositions is possible without deviating from the spirit of theinvention. Someone with ordinary skill in the art of rubber making willfurther understand that considerations for selection of a blowing agentinclude the form (dust, paste, etc.) preferred, and the temperature forvulcanizing a particular rubber formulation. Further, the function andcompounding requirements are specific to each blowing agent composition,and to some extent, to each formulation marketed under the respectiveTradenames listed in the Blue Book. Someone with ordinary skill in theart of rubber making will understand the blowing agent-specific functionand compounding requirements.

The Blue Book identifies a number of Tradenames under which ActivatedAzodicarbonamide can be purchased, including, among others: Celogen 754(Uniroyal Chemical, supplier), Celogen 785A (Uniroyal Chemical,supplier), and Celogen 700 (Uniroyal Chemical, supplier). The Blue Bookidentifies a number of Tradenames under which Azodicarbonamide can bepurchased, including, among others: Celogen AZ (Uniroyal Chemical,supplier), Expancel AZ (Proquitec Industrie, supplier), Porofor ADC/F(Bayer Fibers, Organics & Rubber Division, supplier), Porofor ADC/M(Bayer Fibers, Organics & Rubber Division, supplier), and Unicell D(Dong Jin (USA), supplier). The Blue Book identifies a number ofTradenames under which Modified Azodicarbonamide can be purchased,including, among others: Ficel (Schering Berlin, supplier) and UnicellDX (Dong Jin (USA), supplier). The Blue Book, page 316, identifies theProperties of one Azodicarbonamide composition, marketed under theTradename of Porofor ADC/M as: “SP gr. 1.6. Yellow powder. Decompositiontemp. not below 205° C. Volume of gas released about 220 ml/g.” The BlueBook, page 316, identifies the Function and Compounding of Porofor ADC/Mas: “A nitrogen liberating blowing agent for the manufacture ofodorless, cellular vulcanizates. Especially suitable for the manufactureof articles to be cured at relatively high temperatures (e.g.microcellular profiles in LCM devices).”

The Blue Book identifies a number of Tradenames under which p-toluenesulfonylhydrazide can be purchased, including, among others: Biofoam SH(Rit-Chem supplier); Celogen TSH (Uniroyal Chemical, supplier); ExpencelTSH (Proquitec Industira, supplier); and Unicell H (Dong Jin (USA),supplier). The Blue Book, page 314, describes the properties for one ofthe preceding exemplary TSH blowing agent compositions (Celogen TSH) as:“Sp gr. 1.42. Cream colored crystalline powder. Melting point, 125-150°C. (257-302° F.). Decomposition range, 110-120° C. (230-250° F.). Amountof nitrogen gas, 115 cc/gm STP.” The Blue Book, page 314, furtherdescribes the function and compounding for one of the precedingexemplary TSH blowing agent compositions (Celogen TSH) as: “A lowtemperature blowing agent for NR, SBR, NBR, LLR, CR and silicone rubber.Nitrogen blowing agent; produces odorless cellular rubber goods;nondiscoloring and nonstaining; slightly activating to the cure. CelogenTSH is a superior blowing agent for the expansion of liquid polysulfiderubbers at room temp.”.

The Blue Book identifies a number of Tradenames under which Sodiumbicarbonate can be purchased, including, among others: Dynacarb (LittlemCorporation, supplier). The Blue Book, page 314, describes theproperties for Dynacarb as: “Sp gr. 2.18 free flowing, non-dusting finewhite powder.” The Blue Book, page 314, describes the function andcompounding for Dynacarb as: “Small particle size for sponge compounds.”

The Blue Book identifies a number of Tradenames under which Dinitrosopentamethylene tetramine (DNPT) can be purchased, including, amongothers: Opex (Uniroyal Chemical, supplier), and Unicell G (Dong Jin(USA), supplier). The Blue Book, page 316, describes the properties forOpex as: “DNPT on an inert carrier—80% active. Pale yellow powder. Opexis flammable and should be kept away from all sources of heat, openflame and sparks. Strong acids and acidic salts will cause rapiddecomposition of Opex. Incompatible with oxidizing and reducing agents.”The Blue Book, page 314, describes the function and compounding for Opexas: “Especially effective in pressure procured closed cell applicationsof SBR, CR, NBR and EPDM. Also, imparts a fine cellular structure inextrusion processes. At cure temperature of 130° C. (288° F.) andhigher. Opex and some of its decompositon products show a definite cureactivation in both natural and synthetic rubber sponge. Used in themanufacture of open and closed cell sponge in a wide range of densitieswith uniform cell structure.”

The proportion of the blowing agent used and the particular rubberformulation used determines the final dampening and friction coefficientcharacteristics of the sponge rubber produced. Performancecharacteristics desirable for an intended use of the rubber to beproduced directs the proportion of the blowing agent and the particularrubber formulation to be used.

The hardness of rubber can be measured with a device known in the art asa “durometer.” A standard hardness scale known in the art is the “ShoreA” scale. In an exemplary embodiment of the invention, a rubber with ahardness of approximately 65 to 70 on the Shore A scale is blown with amicro-cellular, closed-cell sponge inducing blowing agent until theresulting sponge rubber has a hardness of approximately 35 to 40 on theShore A scale.

FIG. 1 is a high level flow diagram depicting the logic steps todetermining a proportion of blowing and a rubber formulation with whichto manufacture a rubber for a particular intended purpose. The presentinvention provides for determining 1 a set of performancecharacteristics desirable for an intended use of a pneumatic rubbertire, said set of performance characteristics comprising a resiliencyfactor, a dampening factor, and a relative hardness factor. Then arubber formulation is determined 2 that exhibits a level of rubberresiliency corresponding to said resiliency factor. A blown rubberformulation is then determined 3 that would have a level of dampeningcorresponding to said dampening factor and a hardness measurementcorresponding to said relative hardness factor. The determined rubberformulation is then blown 4 with a micro-cellular, closed-cell spongeinducing blowing agent to produce the blown rubber formulation having alevel of dampening corresponding to said dampening factor and a hardnessmeasurement corresponding to said relative hardness factor. Rubbers thatcould be used would include SBR rubber (a synthetic “natural” rubberavailable from various suppliers), Stealth grade C4 (Supplier: Stone AgeEquipment, Inc., Redlands, Calif., USA), Stealth grade S1 (Supplier:Stone Age Equipment, Inc., Redlands, Calif., USA), and natural rubber(available from various suppliers).

In one exemplary outer tire layer embodiment, blowing agent Celogen AZ(Uniroyal Chemical, supplier) is used to blow Stealth grade C4(Supplier: Stone Age Equipment, Inc., Redlands, Calif., USA) rubber witha hardness of approximately 79 on the Shore A scale down to a hardnessof approximately 40 on the Shore A scale. In a second exemplary outertire layer embodiment, blowing agent Celogen AZ (Uniroyal Chemical,supplier) is used to blow Stealth grade S1 (Supplier: Stone AgeEquipment, Inc., Redlands, Calif., USA) rubber with a hardness ofapproximately 72 down to a hardness of approximately 40 on the Shore Ascale. In a third outer tire layer embodiment, blowing agent Celogen AZ(Uniroyal Chemical, supplier) is used to blow SBR rubber (a synthetic“natural” rubber available from various suppliers) with a hardness ofapproximately 70 on the Shore A scale down to a hardness ofapproximately 40 on the Shore A scale.

For example, in the case of downhill mountain bike racing, a tire,according to the invention, a micro-cellular, closed-cell spongeinducing blowing agent is used to blow a relatively hard, lowresilience, high dampening rubber to create an outer tire layer ofmicrocellular, closed-cell sponge. In an exemplary embodiment of adownhill mountain bike racing tire, a rubber with a hardness ofapproximately 60 to 65 on the Shore A scale is blown with amicro-cellular, closed-cell sponge inducing blowing agent until theresulting sponge rubber has a hardness of approximately 30 to 35 on theShore A scale. Then, according to the invention, the outer tire layer isbonded to a non-stretch or limited-stretch pneumatic tire lining.Non-stretch, or limited-stretch, pneumatic tire linings are often madeof nylon. Techniques for bonding a rubber layer to a non-stretch, orlimited-stretch, nylon pneumatic tire lining are well known in the artof tire making.

In the case of cross-country bicycle racing, a tire with low rollingresistance is desirable. According to the invention, a micro-cellular,closed-cell sponge inducing blowing agent is used to blow a relativelyhard, higher resiliency rubber to create an outer tire layer ofmicro-cellular, closed-cell sponge. In an exemplary embodiment of across-country bicycle racing tire, a rubber with a hardness ofapproximately 70 to 75 on the Shore A scale is blown with amicro-cellular, closed-cell sponge inducing blowing agent until theresulting sponge rubber has a hardness of approximately 40 to 45 on theShore A scale. Then, according to the invention, the outer tire layer isbonded to a non-stretch, or limited stretch, pneumatic tire lining.

In the case of wet surface cycling, it is desirable to maximize surfacecontact. According to the invention, a micro-cellular, closed-cellsponge inducing blowing agent is used to blow a relatively hardnon-sponge rubber to a lower level of hardness on the Shore A scale. Theresult is a sponge rubber with a higher density of micro-cellularclosed-cell gas pockets. In an exemplary embodiment of a wet surfacecycling tire, a rubber with a hardness of approximately 60 to 65 on theShore A scale is blown with a micro-cellular, closed-cell spongeinducing blowing agent until the resulting sponge rubber has a hardnessof approximately 30 to 35 on the Shore A scale. Then, according to theinvention, the outer tire layer is bonded to a non-stretch, orlimited-stretch, pneumatic tire lining.

As part of the vulcanization process for a micro-cellular, closed-cellsponge made according to the present invention, a “skin” will sometimesform on the outer surface of the rubber. Such a skin sometimes has fewermicro-cellular, closed-cell sponge gas pockets than rubber farther fromthe surface. FIG. 2 depicts, under extreme magnification, an unevendistribution of gas pockets. FIG. 2 depicts a reduction in the densityof gas pockets from the interior 5 of the rubber, to the exterior 6 ofthe rubber in an exemplary micro-cellular, closed-cell sponge rubbervulcanization process. In some other alternative micro-cellular,closed-cell sponge rubber vulcanization processes, the density of gaspockets is more or less evenly distributed.

FIG. 3 is a cross-sectional view of an exemplary outer tire mold 10-10′into which rubber is placed to form a tire outer in an exemplaryembodiment of the present invention. As depicted in FIG. 3, a typicaltire mold comprises two separate pieces, e.g., 10 and 10′, that areplaced together. In an exemplary single-rubber outer embodiment of thepresent invention, micro-cellular closed-cell sponge rubber is placed inthe mold to form a tire outer. As one with ordinary skill in the rubberarts will understand, pre-cured rubber is clay-like. To form a tireouter, rubber is placed in a mold, is pressed so that the rubber “flows”into the mold, and is then cured in a vulcanization process.

FIG. 4 is a cross-sectional view of an exemplary single-rubber tireouter 20 in which micro-cellular closed-cell sponge rubber 80 forms atire outer in an exemplary single-rubber tire outer embodiment of thepresent invention. As depicted in FIG. 4, as will be understood bysomeone with ordinary skill in the bicycle tire-making art, a bead,e.g., 30 and 31, such as one made with Kevlar or other aramid fiber, isinserted in the rubber placed in the mold 10 (FIG. 3). Further, asdepicted in FIG. 3, the exemplary mold 10 provides detents 14 with whichto form tire outer protrusions, e.g., 32 and 33 as depicted in FIGS. 4through 7.

Additional modifications and variations of the above-describedembodiments will be apparent to those with ordinary skill in the artwithout departing from the spirit of the invention. For example, it willbe understood by someone with ordinary skill in the art that, withoutdeparting from the spirit of the invention, an outer tire layercomprising multiple types of rubber, each type of rubber provided in oneor more particular areas of the outer surface of the tire, can be madeusing vulcanization. FIG. 5 is a cross-sectional view of an exemplarymulti-rubber tire outer 40 in which hard, non-sponge rubber 60 formsouter tire tread lugs, 70-71 respectively, and micro-cellularclosed-cell sponge rubber 80 forms inner tire tread lugs 50 in a firstexemplary multi-rubber tire outer embodiment of the present invention.

To form the exemplary multi-rubber tire outer 40 depicted in FIG. 5,micro-cellular closed-cell sponge rubber 80 would be placed in the innertire tread lug indentations 11 of the exemplary outer tire mold 10 asdepicted in FIG. 3; hard, non-sponge rubber 60 would be placed in theouter tire tread lug indentations 12 of the exemplary outer tire mold 10as depicted in FIG. 3. The rubber in the mold would then be cured usingvulcanization. The rubbers comprising the micro-cellular closed-cellsponge rubber 80 and the hard, non-sponge rubber 60 would be selectedaccording to criteria known in the art such that the two rubbers 80 and60 would knit together forming long chains of molecules.

One selection criteria for selecting the two rubbers 80 and 60 thatwould knit together would be to blow rubber having the same compositionas the non-sponge rubber 60 with a micro-cellular closed-cell inducingblowing agent to produce the micro-cellular closed-cell sponge rubber80.

FIG. 6 is a cross-sectional view of an exemplary multi-rubber tire outer100 in which hard, non-sponge rubber 60 forms inner tire tread lugs 50and in which micro-cellular closed-cell sponge rubber 80 forms outertire tread lugs 70-71 in a second exemplary multi-rubber tire outerembodiment of the present invention.

Once a tire outer, e.g., 20, 40, 100 has been formed according to thepresent invention, the tire outer, e.g., 20, 40, 100 is bonded to anon-stretch or limited-stretch pneumatic tire lining. The resultingbonded tire assembly 200 as depicted in FIG. 7 can be assembled withother parts, e.g., a tire rim 120 to form a bicycle tire 300 as depictedin FIG. 7. FIG. 7 is a cross-sectional view of an exemplary assembledbicycle tube tire 300 comprising a multi-rubber tire outer 40 bonded toa pneumatic tire lining to form a bonded tire assembly 200 in the firstalternative exemplary embodiment of the present invention. As depictedin FIG. 7, a tube 140 is filled with air to inflate the outer bondedtire assembly 200. In a tubeless pneumatic tire (not pictured), air usedto inflate the outer bonded tire assembly 200 is sealed between the rim120 and the tire outer protrusions 32 and 33.

The present invention further provides a method for manufacturing shoesole outers, e.g., 220 as shown in FIGS. 10-11. The present inventionfurther provides a shoe sole outer, e.g., 220 that is made byvulcanizing micro-cellular closed-cell sponge rubber 222 (as depicted inFIGS. 10-11) formulated from relatively hard non-sponge rubber withnon-sponge rubber 221 (as depicted in FIGS. 10-11) in a shoe sole outermold 210 (as depicted in FIGS. 8-9).

FIG. 8 is a top view of an exemplary shoe mold and FIG. 9 is across-sectional view of a portion of the exemplary shoe mold. In a waysimilar to that described above for placing clay-like uncured rubber ina tire mold, uncured solid rubber would be placed in the shoe sole“tread” indentations 201 in the mold 200; uncured micro-cellularclosed-cell sponge rubber would be placed in the shoe sole mold 200 ontop of the previously placed uncured solid rubber. The rubber would thenbe pressed to flow into the mold. The molded shoe outer would then becured using vulcanization so that non-sponge solid rubber would “knit”with the micro-cellular closed cell sponge rubber. FIG. 10 is across-sectional view of a portion of an exemplary shoe sole outercomprising micro-cellular closed-cell sponge rubber and non-spongerubber. FIG. 11 is a bottom view of an exemplary shoe sole outercomprising micro-cellular closed-cell sponge rubber and non-spongerubber. In an exemplary shoe sole outer embodiment, blowing agentCelogen AZ (Uniroyal Chemical, supplier) is used to blow Stealth gradeS1 (Supplier: Stone Age Equipment, Inc., Redlands, Calif., USA) rubberwith a hardness of approximately 72 down to a hardness of approximately50 on the Shore A scale.

In an alternative exemplary shoe sole outer embodiment, uncuredmicro-cellular closed-cell sponge rubber would be placed in the shoesole “tread” indentations 201 in the mold 200; uncured solid rubberwould be placed in the shoe mold 200 on top of the previously placeduncured micro-cellular closed-cell sponge rubber.

ILLUSTRATIVE EMBODIMENTS

Although the present invention has been described in certain specificembodiments, many additional modifications and variations would beapparent to those skilled in the art. It is, therefore, to be understoodthat this invention may be practiced otherwise than as specificallydescribed. Thus, the embodiments of the present invention describedherein should be considered in all respects as illustrative and notrestrictive, the scope of the invention to be determined by the appendedclaims and their equivalents rather than the foregoing description.

1. A method for manufacturing multi-rubber tire outers, said methodcomprising: vulcanizing a tire outer that comprises an inner surface, anouter surface, a first portion, a second portion, a third portion, afourth portion, and a fifth portion, wherein the first portion of thetire outer extends from a first portion of the inner surface of the tireouter to a first portion of the outer surface of the tire outer, whereinthe first portion of the tire outer consists of micro-cellular,closed-cell sponge rubber formulated from relatively hard solid rubber,wherein the outer surface of the first portion of the tire outercomprises inner tire tread lugs, wherein the second portion of the tireouter extends from a second portion of the inner surface of the tireouter to a second portion of the outer surface of the tire outer,wherein the second portion of the tire outer consists of non-spongerubber, wherein the third portion of the tire outer extends from a thirdportion of the inner surface of the tire outer to a third portion of theouter surface of the tire outer, wherein the third portion of the tireouter consists of non-sponge rubber, wherein the fourth portion of thetire outer comprises rubber and a first tire bead, and wherein the fifthportion of the tire outer comprises rubber and a second tire bead. 2.The method of claim 1, said method further comprising bonding the tireouter to a pneumatic tire lining.
 3. A method for manufacturingmulti-rubber pneumatic tires, said method comprising: (A) blowing arelatively hard solid rubber having a first hardness scale measurementwith a micro-cellular, closed-cell inducing blowing agent to produce amicro-cellular, closed-cell sponge rubber having a second hardness scalemeasurement, wherein the second hardness scale measurement is less thanthe first hardness scale measurement; (B) vulcanizing a multi-rubbertire outer that comprises an inner surface, an outer surface, a firstportion, a second portion, a third portion, a fourth portion, and afifth portion, wherein the first portion of the multi-rubber tire outerconsists of the micro-cellular, closed-cell sponge rubber produced in(A), wherein the first portion of the multi-rubber tire outer extendsfrom a first portion of the inner surface of the multi-rubber tire outerto a first portion of the outer surface of the multi-rubber tire outer,wherein the second portion of the multi-rubber tire outer consists ofnon-sponge rubber, wherein the second portion of the multi-rubber tireouter extends from a second portion of the inner surface of themulti-rubber tire outer to a second portion of the outer surface of themulti-rubber tire outer, wherein the outer surface of the second portionof the multi-rubber tire outer comprises inner tire tread lugs, whereinthe third portion of the multi-rubber tire outer consists ofmicro-cellular, closed-cell sponge rubber produced in (A), wherein thethird portion of the multi-rubber tire outer extends from a thirdportion of the inner surface of the multi-rubber tire outer to a thirdportion of the outer surface of the multi-rubber tire outer, wherein thefourth portion of the multi-rubber tire outer comprises rubber and afirst tire outer edge, wherein the fourth portion of the multi-rubbertire outer further comprises a first tire bead imbedded in the firsttire outer edge, wherein the fifth portion of the multi-rubber tireouter comprises rubber and a second tire outer edge, wherein the fifthportion of the multi-rubber tire outer further comprises a second tirebead imbedded in the second tire outer edge; and (C) assembling a tirecarcass comprising bonding the tire outer of (B) to a pneumatic tirelining.
 4. The method of claim 1 wherein the relatively hard solidrubber has a first hardness scale measurement of approximately 70 to 79on a Shore A scale of hardness and wherein the micro-cellular,closed-cell sponge rubber has a second hardness scale measurement ofapproximately 40 on the Shore A scale of hardness.
 5. The method ofclaim 1 wherein the relatively hard solid rubber has a first hardnessscale measurement of approximately 60 to 65 on a Shore A scale ofhardness and wherein the micro-cellular, closed-cell sponge rubber has asecond hardness scale measurement of approximately 30 to 35 on the ShoreA scale of hardness.
 6. A method for manufacturing pneumatic tires, saidmethod comprising: bonding a tire outer to a pneumatic tire lining,wherein the tire outer comprises an inner surface, an outer surface, afirst edge, a second edge, a first tire bead and a second tire bead,wherein the tire outer extends from the first tire bead embedded in thefirst edge of the tire outer to the second tire bead embedded in thesecond edge of the tire outer, and wherein the tire outer furthercomprises: a first portion of the tire outer consisting ofmicro-cellular, closed-cell sponge rubber formulated from relativelyhard solid rubber, wherein the first portion of the tire outer extendsfrom a first portion of the inner surface of the tire outer to a firstportion of the outer surface of the tire outer; a second portion of thetire outer consisting of non-sponge rubber, wherein the second portionof the tire outer extends from a second portion of the inner surface ofthe tire outer to a second portion of the outer surface of the tireouter; and a third portion of the tire outer consisting of non-spongerubber, wherein the third portion of the tire outer extends from a thirdportion of the inner surface of the tire outer to a third portion of theouter surface of the tire outer, wherein the first portion of the tireouter is between the second portion of the tire outer and the thirdportion of the tire outer.
 7. A pneumatic tire, said pneumatic tirecomprising: (A) a rubber tire outer comprising: 1) a first edge disposedaround a first tire bead, 2) a second edge disposed around a second tirebead, 3) an inner surface, 4) an outer surface, 5) a first portionextending from a first portion of the inner surface of the rubber tireouter to a first portion of the outer surface of the rubber tire outer,wherein the first portion of the rubber tire outer consists ofmicro-cellular, closed-cell sponge rubber formulated from relativelyhard solid rubber, wherein the first portion of the outer surface of thetire outer comprises inner tire tread lugs; 6) a second portionextending from a second portion of the inner surface of the rubber tireouter to a second portion of the outer surface of the rubber tire outer,wherein the second portion of the rubber tire outer consists ofnon-sponge rubber; 7) a third portion extending from a third portion ofthe inner surface of the rubber tire outer to a third portion of theouter surface of the rubber tire outer, wherein the third portion of therubber tire outer consists of non-sponge rubbers wherein the firstportion of the rubber tire outer is disposed in between the secondportion and the third portion; (B) a pneumatic tire lining, wherein theinner surface of the rubber tire outer is bonded to the pneumatic tirelining.
 8. A pneumatic tire, said pneumatic tire comprising: (A) a tireouter comprising: (1) a first edge disposed around a first tire bead,(2) a second edge disposed around a second tire bead, (3) an innersurface comprising a first portion, a second portions and a thirdportion, (4) an outer surface comprising a first portion, a secondportion and a third portion, (5) a first portion of the tire outer thatextends from the first portion of the inner surface of the tire outer tothe first portion of the outer surface of the tire outer, wherein thefirst portion of the tire outer consists of non-sponge rubber, whereinthe first portion of the outer surface of the tire outer comprises innertire tread lugs, (6) a second portion of the tire outer that extendsfrom the second portion of the inner surface of the tire outer to thesecond portion of the outer surface of the tire outer, wherein thesecond portion of the tire outer consists of micro-cellular, closed-cellsponge rubber formulated from relatively hard solid rubber, and (7) athird portion of the tire outer that extends from the third portion ofthe inner surface of the tire outer to the third portion of the outersurface of the tire outer, wherein the third portion of the tire outerconsists of micro-cellular, closed-cell sponge rubber formulated fromrelatively hard solid rubber; and (B) a pneumatic tire lining, whereinthe inner surface of the tire outer is bonded to the pneumatic tirelining.